With reference, for example, to hair transplantation, manual and automatic hair transplantation procedures are known. For example, in a patient having male pattern baldness, hair transplantation typically involves harvesting donor hair grafts from the side and back fringe areas (donor areas) of the patient's scalp, and implanting them in a bald area (recipient area). In one known manual method, a linear portion of the scalp is removed from a donor area by dissection with a scalpel down into the fatty subcutaneous tissue. The strip is dissected (under a microscope) into the “follicular units,” which are then implanted into a recipient area in respective holes or sites made by an implanting tool. Follicular units (also referred to herein as FU or FUs) are naturally occurring aggregates of 1-3 (and much less commonly, 4-5) closely spaced hair follicles that are distributed randomly over the surface of the scalp.
Some of the known automated systems and methods for transplanting hair are disclosed in U.S. Pat. No. 6,585,746 and U.S. Publication No. 2007/0106306, which are hereby incorporated by reference in their entirety. Generally, such automated systems comprise a robotic arm having a harvesting and/or implantation tool mounted on the arm. One or more cameras are also mounted on the arm and are used to image the body surface. A processor is configured to receive and process images acquired by the cameras. A controller is operatively coupled to the processor and the robotic arm. The controller controls the movement of the robotic arm based, at least in part, on the processed images acquired by the cameras and the processor. The arm is controllably moveable to position the tool at a desired orientation and position relative to the body surface to perform harvesting and transplanting hairs.
Hair transplantation requires selecting the follicular units to be harvested and removing them for implanting into a recipient area (e.g., bald area). The follicular units may be classified, or “typed,” based on the number of hair follicles in the unit and identified in shorthand as an “F1” for a single hair follicular unit, an “F2” for a two hair follicular unit and so on for follicular units with 3-5 hairs. In some cases of follicular units comprising multiple hair follicles, the multiple hair follicles may appear to emerge from a single point in the skin. In other cases of follicular units comprising multiple hair follicles, the hair follicles may emerge from or exit the skin surface at slightly spaced apart positions.
Each hair follicle has the following end points. One end point, typically located on the surface of the skin, is called the “tail.” Hair tail is the point from which hair follicle emerges from the skin. Another end point is called the “head” and corresponds to the tip of each hair of the follicular unit lying above the skin surface. Thus, a single-hair follicular unit has one head and one tail, while a two-hair follicular unit has two heads and two tails (although the tails of each hair follicle in some follicular units may emerge from the same point on the skin and appear as one tail only).
For harvesting, it is desirable to know exactly where hairs of the follicular unit emerge from the skin. For example in various automated or image-guided procedures, inaccurate hair tail position determination can adversely impact baseline information for reconstructing hair plane, or affect proper positioning of the tool used in the procedure relative to the hair, which may result in damaging hair graft (e.g. transecting hair follicle during harvesting).
Therefore, there is a need for a more efficient and accurate determination of hair tail position on a body surface.